Get a shallow (sometimes called "pancake") ceiling box that is made to screw into the underside of a joist (it's basically the thickness of the drywall). They are available at HD or most other hardware stores/electrical supply houses. They will easily support a 25# chandelier as you can use long wood screws.

I looked at that, but the issue is I can only get one side (right) of the pancake screwed into the joists. i.e. the pancake would have the desire to pull down on the opposite site since it would not have anything to attach too...

Here is a link that might be useful:

A bracket on the other side, could be wood, metal, anything laying around in your junkpile that would be strong enough to hold the weight.

And then watch out for box fill violations.

If the light canopy is not marked with a volume it does not count.

You can always move the light a few inches.
No one will notice.

The issue is moving it 4" will be VERY obvious. The light is centered under a round island... any movement will be very noticeable since whoever sits to the side it is moved towards will bang there head or at least feel crowded.

I though about a pancake, but again only one side can be screwed in, so the 25lbs light will eventually start pulling down on one side!

"I though about a pancake, but again only one side can be screwed in, so the 25lbs light will eventually start pulling down on one side!"

You cut open the ceiling and add blocking to support the box.

You can always move the island.

Slip a 1/8" x 1" wide peice of metal long enough to span the joists. Dig out the back side of the wallboard to allow you to place the metal up tight to the joists without bumping the wallboard out. Drill a hole at an angle to screw into the joist that barely shows, then drill and screw into the opposite joist. Line up your pancake box, drill and nut and bolt the box to the 1" metal plate.

And hope the AHJ does not notice the very likely box overfill.

Move the box a 1/4 to a 1/2 inch and you can get both joists solidly. Or drive one screw at an angle and leave the box where it is. If there is not a hole handy for the screw you drill another one.

Can't you slip a box in between the joists?

how about...
Fill the gap between the joists and attach a regular box that will hang below the ceiling...now use a small medallion
to cover the protrusion...just a thought.

I can get a switch box between the joists with screws holding it against one of the joists... but is that OK code wise using a switch box vs. outlet???

I am opening the chandelier box now to see if the canopy would allow a flush mounted outlet box with the canopy hiding the remaining portion of the box sticking down from the ceiling.

"I can get a switch box between the joists with screws holding it against one of the joists... but is that OK code wise using a switch box vs. outlet???"

As long as it is deep enough for the box fill all you need is an adapter that uses the device mounting holes to carry the chandelier.